Generally, a motor is operated at a high speed and a low torsion force. In other words, it is difficult to drive a large-sized load. Consequently, for allowing the motor to drive a heavy object, a reducer is used for reducing the rotating speed of the motor and increasing the torsion force.
Conventionally, the reducer and the motor are separate components. It is necessary to connect the reducer with the motor through an additional connection structure such as a shaft coupling or a gear box. In such way, the volume and weight of the overall structure of the reducer and the motor are increased. In other words, the connection structure for connecting the reducer and the motor cannot be applied to the device that requires light weight and compact space. For example, the connection structure is not suitably applied to an industrial robotic arm or a power assisting device.
Nowadays, some reducers are equipped with motors. Under this circumstance, the shaft coupling or the gear box for connecting the reducer and the motor is omitted. However, since this reducer uses a mono-cycloidal set (i.e., a single cycloid), some drawbacks occur. For example, when the reducer is operated at a high speed, it is difficult to maintain the dynamic balance state. Consequently, the operation of the reducer results in high vibration.
Therefore, there is a need of providing a speed reducing device having a power source in order to the address the above issues.